In a screen printing operation of allowing a conductive material in a paste phase (conductive paste: hereinafter, simply referred to as “paste”) to stay in pattern holes formed in a mask and printing a pattern on the surface of a printing medium, the paste remains in the pattern holes at the time of separating the printing medium from the mask after printing and thus the amount of paste printed on the surface of the printing medium becomes lack, thereby causing printing failure. In the past, in order to better pull the paste out of the pattern holes, there have been suggested a method of separating the mask and the printing medium from each other at a very low speed (see Patent Document 1 and Patent Document 2) and a method of performing a plate separating operation in a state where an end of the mask is allowed to move more upward than the other end and a plate separation angle of the mask about the printing medium is kept constant (see Patent Document 3).
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 5-185580
[Patent Document 2] Japanese Unexamined Patent Application Publication No. 8-244203
[Patent Document 3] Japanese Unexamined Patent Application Publication No. 9-314802
However, in the plate separation methods disclosed in Patent Documents 1 and 2, a phenomenon of warping downwardly with the lowering of the printing medium occurs in the mask due to the adhesive force of paste. In addition, since the plate separation is started from an end of the printing medium and the center portion is finally separated, a high-speed plate separation is instantaneously caused at the center portion of the printing medium by an upward resilient restoring force acting on the mask and an operation of pulling out the paste is deteriorated, thereby easily causing printing failure. In the plate separation method disclosed in Patent Document 3, there is a problem in that it is necessary to add a moving mechanism to the mask and the plate separation method is not applicable to a printing apparatus employing a metal mask which has high rigidity and is not deformed easily.